The present invention relates to a device for measuring the displacement of stems of valves; more particularly, the invention relates to an electronic position transmission device adapted to transmit, according to a linear law, the position of the stem of valves, such as adjustment valves or rotary valves.
As it is known, in the field of adjustment valves it is particularly important to know at all time the position of the stem of the valve in order to know the state of the valve time by time.
Position transducers currently used for this purpose suffer the drawback that they do not offer high measurement precision and are further affected by mechanical displacements caused not by the angular movement of the stem of the valve whose position is to be detected but, for example, by thermal expansions.
It is commonly known to use a rotating potentiometer as a position transducer; however, such potentiometer entails the drawback that it has components which are subject to friction wear and also requires shielding for protection against the inevitable sparks generated during its operation.
Another type of position transducer that is currently used is a differential transformer, which however entails the drawback of being expensive.